Heat exchanger for vehicular air conditioning apparatus

ABSTRACT

In an evaporator that constitutes part of a vehicular air conditioning apparatus, a sensor is provided, which is capable of detecting the temperature in the evaporator. In the evaporator, the sensor is installed on a back surface side thereof facing a downstream side, and on a first cooling section, through which air from a first blower unit flows. Also, the sensor is installed at a position in the vicinity of a supply conduit that supplies a coolant medium with respect to the evaporator. At a region where a maximum low temperature in the evaporator occurs, and for which there is a fear of freezing due to moisture contained within the air, the temperature is detected by the sensor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger, which is installed ina vehicular air conditioning apparatus that performs temperatureadjustment of a vehicle compartment, whereby the heat exchanger is usedby the vehicular air conditioning apparatus for cooling and heating ofair that is blown into the vehicle compartment.

2. Description of the Related Art

In a vehicular air conditioning apparatus that is mounted in a vehicle,internal and external air is drawn into a casing by a blower, and aftercooled air, which has been cooled by a heat exchanger that forms acooling means, and heated air, which has been heated by a heat exchangerthat forms a heating means, are mixed together in the casing at apredetermined mixing ratio, the mixed air is blown out from defrosterblow-out ports, face blow-out ports, or foot blow-out ports arranged inthe vehicle compartment, whereby adjustment of temperature and humidityin the vehicle compartment is carried out.

In a vehicular air conditioning apparatus such as described above, forexample, as disclosed in Japanese Laid-Open Patent Publication No.05-124426, a blower unit having a blower, a cooling unit containing anevaporator, and a heating unit containing a heater core are arrangedalong a line, wherein such units are divided in half by a plurality ofpartition plates, which are disposed on a center line thereof. Inaddition, air that is blown out from the blower flows through one of thepassages divided by the partition plates, and after passing through theevaporator and the heater core, is blown out from a first blow-out port,whereas air that flows through the other of the passages divided by thepartition plates, in a similar manner, passes through the evaporator andthe heater core, and is blown out from another second blow-out port thatdiffers from the first blow-out port.

Notwithstanding, with the vehicular air conditioning apparatus accordingto the conventional technique, when air that is taken in from anexternal intake port flows through the evaporator, moisture containedwithin the air freezes when the moisture comes into contact with theevaporator that forms the cooling means. As a result, the ventilationpassageways inside the evaporator become narrowed, and there is aconcern that the cooling effectiveness of the evaporator will bedeteriorated.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a heat exchangerfor use in a vehicular air conditioning apparatus, which is capable ofpreventing freezing in the heat exchanger due to moisture becomingfrozen and adhering to surfaces of the heat exchanger, in order toobtain stable operating characteristics.

In order to achieve the aforementioned object, the present invention ischaracterized by a heat exchanger in a vehicular air conditioningapparatus having a casing including a first passage through whichexternal air flows and a second passage through which internal airflows, and a switching mechanism for switching a flow state of theexternal air and the internal air in the first passage and the secondpassage, wherein the heat exchanger is disposed in the interior of thecasing so as to straddle between the first passage and the secondpassage, for thereby cooling and supplying the external air and theinternal air, the heat exchanger comprising:

a supply member, which is supplied with a coolant medium that circulatesthrough the interior thereof;

a discharge member, through which the coolant medium that has circulatedthrough the interior is discharged;

a first cooling section, which faces the first passage, for performingcooling of the external air that flows through the first passage;

a second cooling section, which faces the second passage, for performingcooling of the internal air that flows through the second passage; and

a sensor for detecting a temperature of the heat exchanger,

wherein the sensor faces toward the first cooling section, and isdisposed at a position proximate to the supply member.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a vehicular air conditioningapparatus according to an embodiment of the present invention;

FIG. 2 is an overall cross sectional view of the vehicular airconditioning apparatus shown in FIG. 1;

FIG. 3 is a cross sectional perspective view taken along line of FIG. 1;

FIG. 4 is an external perspective view of an evaporator shown in FIG. 2;

FIG. 5 is a plan view of the evaporator shown in FIG. 4;

FIG. 6 is an outline view showing the flow of a coolant medium in theevaporator of FIG. 4;

FIG. 7 is an outline structural view showing a casing, first and secondblower units, and an evaporator, which constitute the vehicular airconditioning apparatus of FIG. 1; and

FIG. 8 is an external perspective view showing a modified example of theevaporator shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment concerning a heat exchanger for use in avehicular air conditioning apparatus according to the present inventionshall be explained in detail below with reference to the accompanyingdrawings. In FIG. 1, reference numeral 10 indicates a vehicular airconditioning apparatus according to an embodiment of the presentinvention. The vehicular air conditioning apparatus 10, for example, isinstalled in a vehicle having three rows of seats arranged along thedirection of travel of the vehicle. In the following descriptions, thefirst row of seats in the vehicle compartment of the vehicle isdesignated as front seats, the second row of seats is designated asmiddle seats, and the third row of seats is designated as rear seats.

Further, the vehicular air conditioning apparatus 10 is installed sothat the right-hand side thereof shown in FIG. 2 (in the direction ofarrow A) is oriented toward the front side of the vehicle, whereas theleft-hand side (in the direction of arrow B) is oriented toward the rearside of the vehicle. The arrow A direction shall be described as aforward direction, whereas the arrow B direction shall be described as arearward direction.

In the present embodiment, inside a casing 12, plural rotating membersmade up of dampers or the like are provided, wherein the rotatingmembers are operated by rotational drive sources such as motors or thelike. For purposes of simplification, depictions and explanationsconcerning such rotational drive sources have been omitted.

As shown in FIGS. 1 through 3, the vehicular air conditioning apparatus10 includes the casing 12 constituted by respective air passages, afirst blower unit 16 connected through a connection duct 14 to a sideportion of the casing 12 for taking in air (external and internal air)from outside of the vehicle and from inside the vehicle compartment, andblowing the air toward the front seat side of the vehicle, an evaporator(heat exchanger) 18 arranged inside the casing 12 for cooling air, aheater core 20 for heating air, a second blower unit 22 connected to alower portion of the casing 12 for taking in air from inside the vehiclecompartment (interior air) and blowing the air toward the rear seats ofthe vehicle, and a damper mechanism (switching mechanism) 24 forswitching the flow of air that flows through and inside each of therespective passages.

The casing 12 is constituted by first and second divided casings 26, 28having substantially symmetrical shapes, wherein a center plate 30 isdisposed between the first divided casing 26 and the second dividedcasing 28. The connection duct 14 is connected on a lower side portionof the first divided casing 26, and a first intake port 32 is formedthrough which air is supplied from the first blower unit 16. The firstintake port 32 communicates with a first front passage (first passage)34 disposed on an upstream side of the evaporator 18.

The evaporator 18 is disposed so as to straddle between the firstdivided casing 26 and the second divided casing 28. One end of theevaporator 18 in the forward direction (the direction of arrow A) of thevehicle is inclined downward at a predetermined angle with respect tothe other end thereof in the rearward direction of the vehicle.

As shown in FIGS. 4 and 5, in the evaporator 18, for example, a pair oftubes (first and second tubes) 36 a, 36 b are formed from thin plates ofaluminum or the like, and fins 38, which are folded in a serpentine-likeundulating (wavy) shape, are disposed respectively between the stackedtubes 36 a, 36 b. On the fins 38, a plurality of louvers (not shown) areformed, which are cut out so as to be inclined at predetermined angleswith respect to the planar surface of the fins 38. By causing a coolantmedium L (see FIG. 6) to flow through the interior of the tubes 36 a, 36b, air that passes through the louvers and flows between the fins 38 iscooled by the coolant medium L and is supplied to the downstream side aschilled air.

Further, on opposite ends of the tubes 36 a, 36 b in the evaporator 18,respective hollow first and second tank portions 40 a, 40 b areconnected for retaining a coolant medium L that flows through theinterior of the tubes 36 a, 36 b. Together therewith, thin plate shapedretaining plates 42 a, 42 b are disposed respectively on opposite endsof the first and second tank portions 40 a, 40 b. The retaining plates42 a, 42 b are in parallel with the tubes 36 a, 36 b.

In addition, on the side of the first tank portion 40 a, a supplyconduit (supply member) 46 through which the coolant medium L issupplied from the exterior, and a discharge conduit (discharge member)48 through which the coolant medium L having circulated through theinterior of the evaporator 18, are connected (see FIG. 4). The supplyconduit 46 is formed somewhat smaller in diameter than the dischargeconduit 48.

The supply conduit 46 and the discharge conduit 48 are disposed inparallel in the thickness direction of the evaporator 18, such that whenthe evaporator 18 is arranged inside the casing 12, the dischargeconduit 48 is disposed on a front surface 18 a that faces the firstfront passage 34 on the upstream side, whereas the supply conduit 46 isdisposed on a back surface (side surface) 18 b facing second frontpassages 80 a, 80 b on the downstream side of the evaporator 18.

More specifically, the evaporator 18 is disposed such that the frontsurface 18 a thereof is on the upstream side inside the casing 12,whereas the back surface 18 b is disposed on the downstream side (seeFIG. 2).

Furthermore, the evaporator 18 includes a first cooling section 50disposed on one end side having the first tank portion 40 a, and whichfaces toward the first front passage 34 in the interior of the casing12, and a second cooling section 52 disposed on the other end sidehaving the second tank portion 40 b, and which faces toward alater-described first rear passage (second passage) 130 in the interiorof the casing 12 (see FIG. 2). The first cooling section 50 is arrangedforwardly (in the direction of arrow A) in the casing 12 and cools airsupplied from the first blower unit 16 to the first front passage 34,whereas the second cooling section 52 is arranged rearwardly (in thedirection of arrow B) of the casing 12 and cools air supplied from thesecond blower unit 22 to the first rear passage 130.

Further, a dividing means (not shown) for blocking communication of airbetween the first cooling section 50 and the second cooling section 52is disposed at a boundary portion C between the first cooling section 50and the second cooling section 52 in the evaporator 18. The dividingmeans, for example, may comprise a partition plate which is capable ofdividing the interior of the evaporator 18 into two parts, or apartition member which is capable of being installed from the exteriorof the evaporator 18.

A circulation path of the coolant medium L in the evaporator 18 shallbriefly be described with reference to FIG. 6. Herein, the directionfrom one end side of the first tank portion 40 a on which the supplyconduit 46 and the discharge conduit 48 are disposed to the other endside shall be described as a rearward direction (the direction of arrowD1), whereas the direction from the other end side of the first tankportion 40 a to the one end side shall be described as a forwarddirection (the direction of arrow D2).

First, the coolant medium L, which is introduced from the supply conduit46, flows downwardly (in the direction of arrow E1) from the first tankportion 40 a through the tubes 36 b on the back surface 18 b in theevaporator 18. At this time, in the interior of the first tank portion40 a, since first guide walls 54 in parallel with the retaining plates42 a, 42 b are disposed therein, the coolant medium L is guideddownwardly through the tubes 36 b by the first guide walls 54, withoutflowing in the rearward direction (the direction of arrow D1) beyond thefirst guide walls 54. In addition, the coolant medium L, which hasreached the second tank portion 40 b disposed downwardly therefrom,flows in the rearward direction along the second tank portion 40 b, isguided to the tubes 36 b by second guide walls 56 in parallel with theretaining plates 42 a, 42 b, and then is guided upwardly (in thedirection of arrow E2) through the tubes 36 b.

Next, the coolant medium L, which has flowed upwardly, then flowsrearwardly (in the direction of arrow D1) in the evaporator 18 insidethe first tank portion 40 a. Then, after flowing downwardly (in thedirection of arrow E1) through the tubes 36 b and being guided into thesecond tank portion 40 b, flows to the front surface 18 a side of theevaporator 18. Further, after passing through the tubes 36 a disposed onthe front surface 18 a side of the evaporator 18 and flowing upwardly(in the direction of arrow E2), the coolant medium L flows toward theforward side (in the direction of arrow D2) inside the first tankportion 40 a and once again flows downwardly (in the direction of arrowE1) through the tubes 36 a. Since the coolant medium L is prevented fromflowing in the forward direction (the direction of arrow D2) by thefirst guide walls 54, the coolant medium L is guided downwardly (in thedirection of arrow E1) by the first guide walls 54 without flowingtoward the forward side beyond the first guide walls 54.

Lastly, the coolant medium L, which has been guided downwardly into thesecond tank portion 40 b, after having flowed to the forward side (inthe direction of arrow D2) and then upwardly along the tubes 36 a,reaches the first tank portion 40 a and is discharged from the dischargeconduit 48.

In this manner, the coolant medium L, which has been guided from thesupply conduit 46 to the interior of the evaporator 18, and after havingflowed mutually up and down in the rearward direction (the direction ofarrow D1) on the back surface 18 b side, is circulated toward the frontsurface 18 a side, flows mutually up and down in the forward direction(the direction of arrow D2), whereupon the coolant medium L isdischarged from the discharge conduit 48. At this time, air suppliedfrom the upstream side into the evaporator 18 is cooled effectively bythe coolant medium L that flows through the tubes 36 a, 36 b and bypassing over the fins 38, and the cooled air then flows toward thedownstream side.

As shown in FIG. 5, on the evaporator 18 in which the coolant medium Lis circulated, a sensor 58 is disposed for detecting the surfacetemperature of the evaporator 18. The sensor 58 is constituted from amain body portion 60 for detecting temperature, which is attached to theevaporator 18, and a cable 62 that is connected to the main body portion60. Additionally, the sensor 58 is connected via the cable 62 to anon-illustrated controller, whereby the surface temperature of theevaporator 18 detected by the sensor 58 is output as a detection signalto the controller.

The sensor 58, for example, is installed at a region S1 where thetemperature is lowest, and where there is a fear that generation offreezing due to adhered moisture will occur, and serves to detect thesurface temperature in the evaporator 18. Stated otherwise, bycontinuously detecting the surface temperature on the evaporator 18, thesensor 58 is provided with the object of avoiding generation of freezingcaused by the adherence of moisture on the evaporator 18 whenmoisture-containing air passes through the evaporator 18.

Accordingly, the sensor 58, for example, is arranged within the regionS1 on the back surface 18 b side of the evaporator 18 which is suppliedwith a low temperature coolant medium L from the supply conduit 46, andfurther, which is in the vicinity of the supply conduit 46. In addition,the region S1 is on the side of the first cooling section 50 that facestoward the first front passage 34 and the second front passages 80 a, 80b, to which air containing a comparatively large amount of moisture issupplied from the first blower unit 16. The region S1, for example, is aregion surrounded by an imaginary line F drawn in a perpendiculardirection to the lengthwise direction of the first tank portion 40 a ata position where the first guide walls 54 in the first tank portion 40 aconstituting the evaporator 18 are disposed, and the boundary portion Cbetween the first cooling section 50 and the second cooling section 52,and is an area on the side of the supply conduit 46.

More specifically, in the evaporator 18, a position in the vicinity ofthe supply conduit 46 on the back surface 18 b side in the first coolingsection 50 forms a position of maximum low temperature caused by thecoolant medium L, as well as a region where high humidity air,containing a large amount of moisture therein, flows. Therefore, theposition is a region S1 where freezing easily occurs, and at whichdetection of temperature by the sensor 58 is required.

Stated otherwise, for example, on the back surface 18 b side of theevaporator 18, the coolant medium L, which has undergone heat exchangein the evaporator 18 and is raised in temperature, flows through aregion S2 that lies outside of the region S1 where the sensor 58 isdisposed, and in the second cooling section 52 only air (internal air)from inside the vehicle compartment, for which the contained amount ofmoisture therein is low in comparison with the air supplied from thefirst blower unit 16, is supplied from the second blower unit 22. Owingthereto, at the region S2, since the temperature of the coolant medium Lis comparatively high, and further, the possibility of moisture becomingadhered thereto is low, the likelihood of freezing in the evaporator islow.

Further, as understood from the circulation path of the coolant mediumL, which is shown in FIG. 6, because the front surface 18 a side of theevaporator 18 is constructed such that the coolant medium L, which hasflowed through the back surface 18 b of the evaporator 18 and hasundergone heat exchange, then flows through the front surface 18 a, thepossibility of the front surface 18 a side undergoing freezing (i.e.,developing frost thereon) is lowered, due to the coolant medium L havingbeen raised in temperature.

On the other hand, as shown in FIGS. 1 to 3, on the downstream side ofthe evaporator 18, second front passages 80 a, 80 b are formed, throughwhich air having passed through the first cooling section 50 issupplied. Upwardly of the second front passages 80 a, 80 b, a thirdfront passage 82 and a fourth front passage 84 are formed in a branchingor bifurcated manner. Further, in the second front passages 80 a, 80 b,a first air mixing damper 86 is rotatably disposed so as to face towardthe branching portion of the third front passage 82 and the fourth frontpassage 84.

Additionally, by rotation of the first air mixing damper 86, the blowingcondition and blowing rate of cooled air that has passed through theevaporator 18 into the third front passage 82 and the fourth frontpassage 84 is adjusted. The third front passage 82 is arranged on theforward side (in the direction of arrow A), whereas the fourth frontpassage 84 is arranged on the rearward side (in the direction of arrowB) of the casing 12. The heater core 20 is disposed on a downstream sideof the fourth front passage 84.

Further, on the forward side (in the direction of arrow A) of the thirdfront passage 82, a bypass passage 88 is formed, which extends along thethird front passage 82 and supplies air to a later-described mixingsection 98 from the downstream side of the evaporator 18, and a bypassdamper 90 is disposed on a downstream side of the bypass passage 88. Thebypass passage 88 is provided to supply cool air cooled by theevaporator 18 directly to the downstream side under a switching actionof the bypass damper 90.

The heater core 20, similar to the evaporator 18, is disposed so as tostraddle between the first divided casing 26 and the second dividedcasing 28. One end of the heater core 20 in the forward direction (thedirection of arrow A) of the vehicle is inclined downward at apredetermined angle with respect to the other end thereof in therearward direction (the direction of arrow B) of the vehicle. The heatercore 20 includes a first heating section 92, which faces the fourthfront passage 84 and heats air supplied from the fourth front passage84, and a second heating section 94, which faces the later describedthird rear passage 148 and heats air supplied from the third rearpassage 148.

On the downstream side of the heater core 20, a fifth front passage 96is formed. The fifth front passage 96 extends in the forward direction,and at a location that merges with the downstream side of the thirdfront passage 82, the mixing section 98 is formed, in which cooled airsupplied through the third front passage 82 and warm air suppliedthrough the fifth front passage 96 are mixed. A defroster blow-out port100 opens upwardly of the mixing section 98, and to the side of themixing section 98, a rearwardly extending sixth front passage 102 isformed.

Further, in the mixing section 98, a defroster damper 104 is rotatablydisposed, facing the defroster blow-out port 100. By rotation of thedefroster damper 104, the blowing state of air into the defrosterblow-out port 100 and the sixth front passage 102 is switched, and theblowing rate thereof is adjusted.

In the sixth front passage 102, a first vent blow-out port 106 opensupwardly, and a vent damper 108 is rotatably disposed facing toward thefirst vent blow-out port 106, and communicating with a seventh frontpassage 110, which extends further rearwardly. By rotation of the ventdamper 108, the blowing state of air from the mixing section 98 isswitched to the first vent blow-out port 106 and the seventh frontpassage 110, and further, the blowing rate of the air is capable ofbeing adjusted.

The defroster blow-out port 100 and the first vent blow-out port 106open respectively upwardly of the casing 12. The defroster blow-out port100 is arranged on a forward side (in the direction of arrow A), whereasthe first vent blow-out port 106 is arranged on the rearward side (inthe direction of arrow B), substantially centrally in the casing 12 withrespect to the defroster blow-out port 100.

On a downstream side of the seventh front passage 110, a first heatpassage 112 is connected, which extends in the widthwise direction ofthe casing 12 and blows air through a non-illustrated first heatblow-out port in the vicinity of the feet of passengers in the frontseats in the vehicle compartment. Together therewith, a second heatpassage 114 is connected, which extends rearwardly of the casing 12 andblows air through a second heat blow-out port (not shown) in thevicinity of the feet of passengers in the middle seats inside thevehicle compartment.

The first blower unit 16 includes an intake damper 118 in which a duct116 for introducing external air is disposed in an inlet openingthereof, for carrying out switching of internal and external air, and afirst blower fan 120 for supplying to the interior of the casing 12 air(external air or internal air) that is taken in from the duct 116 or thelike. A blower case 122 in which the first blower fan 120 isaccommodated communicates with the interior of the casing 12 via theconnection duct 14 connected to the first intake port 32. The rotationof the first blower fan 120 is controlled by a first blower motor 121,which is driven by supplying electrical power thereto.

In this manner, air supplied from the first blower unit 16 is introducedto the interior of the casing 12 through the connection duct 14 and thefirst intake port 32, and by rotating actions of the first air mixingdamper 86, the defroster damper 104, the vent damper 108 and the bypassdamper 90, which collectively make up the damper mechanism 24, air isselectively supplied through the first through seventh front passages74, 80 a, 80 b, 82, 84, 96, 102, 110, and the bypass passage 88 into thedefroster blow-out port 100, the first vent blow-out port 106 and thefirst and second heat passages 112, 114, which are capable of blowingair to the front and middle seats in the vehicle.

On the other hand, on a lower portion of the casing 12, a second intakeport 128 through which air is supplied from the second blower unit 22 isformed on a rearward side (in the direction of arrow B) perpendicular tothe first intake port 32. The second intake port 128 opens at a positionon an upstream side of the evaporator 18 and communicates with the firstrear passage 130.

The first rear passage 130 is separated from the first front passage 34by a first dividing wall 132, and a rotatable ventilation-switchingdamper (switching damper) 136 is provided between a communicationopening 134 formed in the first dividing wall 132 and the second intakeport 128. In addition, in the case that a mode is selected in whichblowing of air from the second blower unit 22 is halted and blowing ofair only from the first blower unit 16 is carried out, by blocking thesecond intake port 128 by the ventilation-switching damper 136 (i.e.,the state shown by the two-dot-dash line in FIG. 2), back flowing of airinto the second blower unit 22 can be prevented when a portion of theair supplied from the first blower unit 16 passes through the interiorof the evaporator 18 and the heater core 20 and is leaked out to theside of the first through fourth rear passages 130, 142 a, 142 b, 148,150. Thus, noise generated by the second blower unit 22 due to the backflowing of air is prevented. Also, the air that has reached the secondblower unit 22, i.e., unnecessary air, is prevented from flowing intothe vehicle compartment, and an unpleasant sensation is prevented frombeing imparted to passengers in the vehicle.

In this case, as shown in FIG. 7, by rotating the ventilation-switchingdamper 136 to the side of the second intake port 128 and opening thecommunication opening 134, a portion of the air supplied to the firstfront passage 34 can be supplied to the side of the first rear passage130. The driving and controlling of the ventilation-switching damper 136will be described later.

The second blower unit 22 includes a second blower fan 138 that takes inair (internal air) from the vehicle compartment and supplies the intakeair to the interior of the casing 12. A blower case 140 in which thesecond blower fan 138 is accommodated is connected to the second intakeport 128 of the casing 12 and communicates with the first rear passage130. The second blower fan 138, similar to the first blower fan 120, iscontrolled by a second blower motor 141, which is driven by supplyingelectrical power thereto.

On a downstream side of the first rear passage 130, second rear passages142 a, 142 b are formed to which air that has passed through the secondcooling section 52 of the evaporator 18 is supplied. The second rearpassages 142 a, 142 b are separated from the second front passages 80 a,80 b by a second dividing wall 144, and the second dividing wall 144extends to the evaporator 18. Owing thereto, on a downstream side of theevaporator 18, air that has passed through the first rear passage 130and flows to the second cooling section 52 of the evaporator 18 does notintermix mutually with air that has passed through the first frontpassage 34 and flows to the first cooling section 50 of the evaporator18.

Herein, as shown in FIG. 3, the second rear passages 142 a, 142 b, thesecond front passages 80 a, 80 b and the first vent blow-out port 106are separated respectively on sides of the first and second dividedcasings 26, 28 about the center plate 30, which is disposed in thecenter of the casing 12, thereby forming the second rear passage 142 aand the second rear passage 142 b, the second front passage 80 a and thesecond front passage 80 b, and the first vent blow-out port 106 a andthe first vent blow-out port 106 b. Furthermore, as shown in FIG. 4, apair of communication switching dampers 146 a, 146 b, which are capableof switching a communication state between the second rear passage 142 aand the second front passage 80 a, and between the second rear passage142 b and the second front passage 80 b, are disposed in the second rearpassage 142 a and the second rear passage 142 b, respectively, whereinone of the communication switching dampers 146 a and the other of thecommunication switching dampers 146 b are rotatably controlledseparately and independently from each other.

In addition, by rotation of the pair of communication switching dampers146 a, 146 b, the second rear passages 142 a, 142 b for blowing air tothe middle seats and rear seats in the vehicle compartment are placed incommunication mutually with the second front passages 80 a, 80 b forblowing air to the front seats in the vehicle compartment. For example,by changing the rotation amount of one of the communication switchingdampers 146 a and the rotation amount of the other communicationswitching damper 146 b, respectively, the blowing rate of air that isblown from the first vent blow-out port 106 a through the second frontpassage 80 a to the passenger's side in the front seats, and the blowingrate and temperature of air that is blown from the first vent blow-outport 106 b through the second front passage 80 b to the driver's side inthe front seats, can be controlled separately from each other.

The third rear passage 148 facing the heater core 20 is formed on thedownstream side of the second rear passages 142 a, 142 b. One side ofthe third rear passage 148 opens into the heater core 20, whereasanother side thereof opens onto the side of an adjacent fourth rearpassage 150. In addition, a second air mixing damper 152, which mixes ata predetermined mixing ratio the cool air and warm air supplied to thethird rear passage 148, thereby producing mixed air, is disposedrotatably in the third rear passage 148. The second air mixing damper152 switches the communication state between the third rear passage 148and the upstream or downstream side of the fourth rear passage 150,which is connected to the downstream side of the heater core 20.Consequently, air cooled by the evaporator 18 and supplied to the thirdrear passage 148, and air heated by the heater core 20 and that flows tothe fourth rear passage 150, are mixed at a predetermined mixing ratioinside the fourth rear passage 150 by rotation of the second air mixingdamper 152, and are blown out therefrom. Specifically, an intermediatelocation of the fourth rear passage 150 functions as a mixing section,for mixing cool air and warm air that is blown to the middle seats andrear seats in the vehicle.

The fourth rear passage 150 bends so as to circumvent the other end ofthe heater core 20 and extends to communicate with fifth and sixth rearpassages 154, 156, which branch on a downstream side thereof. Arotatable mode switching damper 158 is disposed at the branchinglocation of the fifth and sixth rear passages 154, 156. Thecommunication state between the fourth rear passage 150 and the fifthand sixth rear passages 154, 156 is switched by rotation of the modeswitching damper 158.

The fifth and sixth rear passages 154, 156 extend respectively in therearward direction (the direction of arrow B) of the vehicle. The fifthrear passage 154 communicates with a second vent blowout port (notshown) for blowing air in the vicinity of the faces of passengers in themiddle seats in the vehicle. On the other hand, the sixth rear passage156 communicates with third and fourth heat blow-out ports (not shown)for blowing air in the vicinity of the feet of passengers in the middleand rear seats.

More specifically, air supplied from the second blower unit 22 isintroduced to the interior of the casing 12 through the second intakeport 128, and under rotating actions of the second air mixing damper 152and the mode switching damper 158, which make up the damper mechanism24, the air passes through the first through sixth rear passages 130,142 a, 142 b, 148, 150, 154, 156 and is supplied selectively to thesecond vent blow-out port, and the third and fourth heat blow-out ports(not shown), which are capable of blowing air to the middle and rearseats in the vehicle.

The aforementioned second through sixth front passages 80 a, 80 b, 82,84, 96, 102, the bypass passage 88 and the second rear passages 142 a,142 b are disposed respectively so as to straddle between the firstdivided casing 26 and the second divided casing 28. However, thesepassages also are divided by the center plate 30, which is disposed inthe center of the casing 12.

The vehicular air conditioning apparatus 10 to which the heat exchangeraccording to the embodiment of the present invention is applied isbasically constructed as described above. Next, operations and effectsof the invention shall be explained.

First, when operation of the vehicular air conditioning apparatus 10 isstarted, the first blower fan 120 of the first blower unit 16 is rotatedby supplying electrical power thereto, and air (interior or exteriorair) that is taken in through the duct 116 or the like is supplied tothe first front passage 34 of the casing 12 through the connection duct14. Simultaneously, air (interior air), which is taken in by rotation ofthe second blower fan 138 of the second blower unit 22 by supplyingelectrical power thereto, is supplied to the first rear passage 130 fromthe blower case 140 while passing through the second intake port 128. Inthe following descriptions, air supplied to the interior of the casing12 by the first blower fan 120 shall be referred to as “first air,” andair supplied to the interior of the casing 12 by the second blower fan138 shall be referred to as “second air.”

The first air and the second air supplied to the interior of the casing12 are each cooled by passing respectively through the first and secondcooling sections 76, 78 of the evaporator 18, and flow respectively aschilled air to the second front passages 80 a, 80 b and the second rearpassages 142 a, 142 b, in which the first and second air mixing dampers86, 152 are disposed.

In the case that a vent mode, for example, is selected by a passengerfor blowing air in the vicinity of the faces of passengers, the firstair mixing damper 86 is rotated to an intermediate position between thethird front passage 82 and the fourth front passage 84, whereupon thefirst air (cooled air) supplied to the third front passage 82 flows intothe mixing section 98, and the first air supplied to the fourth frontpassage 84 is heated by passing through the heater core 20 to becomeheated air, and flows into the mixing section 98 through the fifth frontpassage 96, whereby the first cooled air and the first heated air aremixed together.

The first air (mixed air), which is made up of the cool air and heatedair mixed in the mixing section 98, passes through the sixth frontpassage 102 and is blown in the vicinity of the faces of passengers inthe front seats in the vehicle compartment from the first vent blow-outport 106, due to the fact that the defroster blow-out port 100 isblocked by the defroster damper 104, and further, the opening of theseventh front passage 110 is blocked by the vent damper 108.

On the other hand, the second air mixing damper 152 is rotated to anintermediate position in the interior of the third rear passage 148,whereupon the second air (cooled air) supplied to the third rear passage148 is heated by passing through the heater core 20 to become heatedair, and flows to the downstream side through the fourth rear passage150. Together therewith, cooled second air is supplied directly into thefourth rear passage 150 from the opening of the third rear passage 148,is mixed together with the heated second air, and flows to thedownstream side. In addition, under a switching action of the modeswitching damper 158, the second air (mixed air) passes through thefifth rear passage 154 and is blown in the vicinity of the faces ofpassengers in the middle seats in the vehicle compartment from thesecond vent blowout port (not shown).

Next, in the case that a bi-level mode is selected for blowing air inthe vicinity of the faces and feet of passengers in the vehiclecompartment, the first air mixing damper 86 is rotated somewhat towardthe side of the third front passage 82, whereas the vent damper 108 isplaced in an intermediate position, rotated somewhat to the side of thefirst vent blow-out port 106 compared to the case of the vent mode.Additionally, the cooled first air that has passed through theevaporator 18 is supplied directly into the mixing section 98 via thebypass passage 88, is mixed in the mixing section 98 with the first air(mixed air) that is supplied through the third and fifth front passages82, 96, and is blown in the vicinity of the faces of passengers from thefirst vent blow-out port 106. Further, a portion of the first air (mixedair), which flows to the sixth front passage 102 from the mixing section98, passes through the sixth and seventh front passages 102, 110 and issupplied respectively to the first and second heat passages 112, 114,whereby the air is blown in the vicinity of the feet of passengers inthe front and middle seats in the vehicle compartment from the first andsecond heat blow-out ports (not shown).

At the same time, the second air mixing damper 152 is rotated somewhatin a direction away from the heater core 20, and the mode switchingdamper 158 is rotated from the position closing the sixth rear passage156 to an intermediate position between the fifth rear passage 154 andthe sixth rear passage 156. In addition, as for the second air, heatedair heated by the heater core 20 and cooled air, which is supplied tothe fourth rear passage 150 through the opening from the third rearpassage 148, are mixed together and blown as mixed air from the fifthrear passage 154, through the second vent blow-out port, and in thevicinity of the faces of passengers riding in the middle seats in thevehicle compartment, while also being blown from the sixth rear passage156, past the third and fourth heat blow-out ports, and in the vicinityof the feet of passengers riding in the middle and rear seats in thevehicle compartment.

Next, in the case that the heat mode is selected for blowing air in thevicinity of the feet of passengers in the vehicle compartment, the firstair mixing damper 86 is rotated further to the side of the third frontpassage 82 compared to the case of the bi-level mode, while thedefroster damper 104 and the vent damper 108 are rotated respectively toblock the defroster blow-out port 100 and the first vent blow-out port106. Consequently, the first air (mixed air), which was mixed in themixing section 98, passes through the sixth and seventh front passages102, 110 and flows rearwardly to be supplied respectively to the firstand second heat passages 112, 114, and is blown in the vicinity of thefeet of passengers in the front and middle seats in the vehiclecompartment from the non-illustrated first and second heat blow-outports.

On the other hand, the second air mixing damper 152 is rotated furthertoward the side of the opening compared to the case of the bi-levelmode, and further, the mode switching damper 158 is positioned to blockthe fifth rear passage 154. Consequently, the second air (mixed air),which is mixed in the fourth rear passage 150, passes from the fourthrear passage 150, through the sixth rear passage 156, and is supplied tothe third and forth heat blow-out ports, whereby the air is blown in thevicinity of the feet of passengers in the middle and rear seats in thevehicle compartment.

Next, an explanation shall be made concerning a heat-defroster mode forblowing air in the vicinity of the feet of passengers in the vehiclecompartment, as well as for blowing air in the vicinity of a frontwindow for eliminating fog (condensation) from the front window. In theevent that the heat-defroster mode is selected, the defroster damper 104is rotated in a direction to separate from the defroster blow-out port100, so as to assume an intermediate position between the defrosterblow-out port 100 and the opening of the sixth front passage 102, andtogether therewith, the first vent blow-out port 106 is blocked by thevent damper 108 (i.e., the condition of the two-dot-dash line shown inFIG. 2). Consequently, a portion of the first air (mixed air), which ismixed in the mixing section 98, passes through the defroster blow-outport 100 and is blown in the vicinity of the front window of thevehicle, while another portion of the first air flows past the sixth andseventh front passages 102, 110 and is blown in the vicinity of the feetof passengers in the front and middle seats in the vehicle compartmentfrom the first and second heat passages 112, 114 and the first andsecond heat blow-out ports (not shown).

On the other hand, in the heat-defroster mode, in the case that thesecond air is blown toward the middle seats and rear seats of thevehicle compartment, since this mode is the same as the heat modediscussed above, detailed explanations thereof shall be omitted.

Lastly, the defroster mode for blowing air only in the vicinity of thefront widow for eliminating fog (condensation) from the front window inthe vehicle shall be described. In this case, the defroster damper 104is rotated to separate from the defroster blow-out port 100 while theopening of the sixth front passage 102 is blocked, and the first air(mixed air) is supplied from the mixing section 98 to the openeddefroster blow-out port 100 and is blown in the vicinity of the frontwindow in the vehicle. In this case, the defroster mode can be handledsolely by blowing first air supplied only from the first blower unit 16,without driving the second blower unit 22.

In the foregoing manner, according to the present embodiment, when thesensor 58 is installed, which is capable of detecting the surfacetemperature on the evaporator 18, the sensor 58 is disposed within aregion S1 on the evaporator 18, which is in the vicinity of the supplyconduit 46 through which the low temperature coolant medium L issupplied, and on the back surface 18 b side of the evaporator 18 on theside of the supply conduit 46, as well as on the side of the firstcooling section 50 that faces the first front passage 34, to whichexternal air containing a comparatively large amount of moisture issupplied from the first blower unit 16. Consequently, the sensor 58 iscapable of detecting the temperature of a region of maximum lowtemperature in the evaporator 18, where there is a fear that freezingcaused by adhered moisture is likely to occur.

As a result, for example, by outputting the detected temperaturedetected by the sensor 58 to an unillustrated controller and monitoringthe temperature continuously, it becomes possible for freezing, which iscaused by moisture adhered to the front surface 18 a and back surface 18b of the evaporator 18, to be prevented reliably, and narrowing ofventilation passages inside the evaporator 18 due to such freezing withconsequent deterioration in the cooling effectiveness of the evaporator18 is avoided. Owing thereto, a stable cooling capacity is alwaysobtained in the evaporator 18.

In the above embodiment, a case has been described in which the supplyconduit 46 and the discharge conduit 48 are disposed on the first tankportion 40 a constituting the evaporator 18, and together therewith, thefirst cooling section 50 is disposed on the side of the first tankportion 40 a, and a region S1 for arrangement of the sensor 58 is set inthe vicinity of the first tank portion 40 a and the supply conduit 46.However, as shown in FIG. 8, if the supply conduit 46 and the dischargeconduit 48 are disposed on the second tank portion 40 b constituting anevaporator 200, and the first cooling section 50 is disposed on the sideof the second tank portion 40 b, in this case, the region S1 forarrangement of the sensor 58 is on the side of the back surface 18 b ofthe evaporator 200, and lies in the vicinity of the second tank portion40 b and the supply conduit 46 in the first cooling section 50.

More specifically, the region S1 for positioning the sensor 58 is on theside of the back surface 18 b of the evaporator 18, 200 facing one ofthe tubes 36 b to which the coolant medium L is supplied from the supplyconduit 46, and also on the first cooling section 50 on the side of thefirst front passage 34 to which external air is supplied, while inaddition, the region S1 is set at a position in the vicinity of thesupply conduit 46 to which the chilled coolant medium L is supplied.

The heat exchanger for use in vehicular air conditioning apparatusaccording to the present invention is not limited to the above-describedembodiments, and it is a matter of course that various modified oradditional structures could be adopted without deviating from theessence and gist of the invention.

1. A heat exchanger for use in a vehicular air conditioning apparatushaving a casing including a first passage through which external airflows and a second passage through which internal air flows, and aswitching mechanism for switching a flow state of the external air andthe internal air in the first passage and the second passage, whereinthe heat exchanger is disposed in the interior of the casing so as tostraddle between the first passage and the second passage, for therebycooling and supplying the external air and the internal air, the heatexchanger comprising: a supply member, which is supplied with a coolantmedium that circulates through the interior thereof; a discharge member,through which the coolant medium that has circulated through theinterior is discharged; a first cooling section, which faces the firstpassage, for performing cooling of the external air that flows throughthe first passage; a second cooling section, which faces the secondpassage, for performing cooling of the internal air that flows throughthe second passage; and a sensor for detecting a temperature of the heatexchanger, wherein the sensor faces toward the first cooling section,and is disposed at a position proximate to the supply member.
 2. Theheat exchanger for use in a vehicular air conditioning apparatusaccording to claim 1, wherein: the heat exchanger further comprises aplurality of first and second tubes, which are disposed in parallelalong a direction of flow of the air that flows through the interior ofthe casing, and through which the coolant medium flows through theinterior thereof; and the sensor is disposed on a side surface of theheat exchanger that faces toward either of the first tubes or the secondtubes, which communicate with the supply member, and to which thecoolant medium is supplied from the supply member.